The present disclosure relates to a recording device using a self excited oscillation semiconductor laser as a light source for recording and to an optical oscillator device using a self excited oscillation semiconductor laser.
A laser light with a high peak power, in particular an intense pulsed light is very effective for a nonlinear multiphoton absorption process.
Using this absorption process, applications to three dimensional optical recording, ultra microfabrication, nondestructive bioimaging, or the like are expected.
For example, there is reported a method for multilayer recording by irradiating a high power laser light to a transparent bulk material having a nonlinear effect (refer to Seiji Kobayashi, Kimihiro Saito, Takashi Iwamura, Hisayuki Yamatsu, Toshihiro Horigome, Mitsuaki Oyamada, Kunihiko Hayashi, Daisuke Ueda, Norihiro Tanabe and Hirotaka Miyamoto, ISOM 2009 Digest Th-1-01, 2009).
This method shows a possibility for an inexpensive and high capacity recording medium compared to a stacked disk in the past.
As a light source to emit a high power laser light, a mode locked titanium sapphire laser is used. In the example of the above ISOM 2009 Digest Thl-01 as well, a light of 810 nm emitted from a titanium sapphire laser is converted into a wavelength of 405 nm by a SHG (second harmonic generator) to be a light source for short wavelength recording that is advantageous for high density recording.
In a case of such a large and expensive solid state laser, it is limited to be applied to experiments in a laboratory (for example, refer to Spectra-Physics KK., [online], [searched on Aug. 6, 2010], Internet URL: http://www.spectra-physics.jp/member/admin/document_upload/Tsunami_Series_Data_Sheet.pdf).
With that, many researchers are trying to develop a pulsed light source that is much smaller in size and stable for practical use on a semiconductor basis.
In optical recording of next generation as the previously mentioned methods, a blue-violet laser light source is strongly desired that is advantageous for high density recording in all semiconductors.
For example, it is reported that, in a case of carrying out 1 MHz repetition due to strong excitation driving in a gain switching laser, a peak power of 55 W is attained (refer to M. Kuramoto, T. Oki, T. Sugahara, S. Kono, M. Ikeda, and H. Yokoyama, Appl. Phys. Lett. 96, 051102—2010_.).
It should be noted that, due to a demand for a high data transmission rate in the market, an even higher repetition frequency is desired in a light source for data recording as well.
A self excited oscillation GaN blue-violet semiconductor laser attains a light source that is capable of an oscillation output with a pulse width of 30 ps and 2.4 W at a frequency of 0.9 GHz (refer to Takao Miyajima, Hideki Watanabe, Masao Ikeda and Hiroyuki Yokoyama, Applied Physics Letters 94, 161103 (2009)).
This semiconductor laser is a BS (bisectional) self excited oscillation semiconductor laser configured with a gain section and a saturable absorber section.
In this semiconductor laser, a reverse bias voltage is applied to the saturable absorber section. At this time, by injecting a current to the gain section, a laser light at a wavelength of 407 nm, for example, is emitted.
In a recording and reproducing device, data is supposed to be recorded at an arbitrary location based on address information, such as a wobble signal read out of an optical recording medium. In a case of using such a self excited oscillation laser for recording, it is desired to modulate in accordance with recording data, and at the same time, to record while synchronizing a pulse of the self excited oscillation with the modulation.